In general, radar tri-lateralization position locators are utilized in navigation and the like to determine the position of ships relative to two or more fixed shore stations. The baseline or distance between the two stations must always be included in the position calculations. In these types of prior art devices the shore stations are never moved and, may include, a relatively large number of stations positioned along a shore or navigation course so that a ship may use signals from different stations along its course to determine its position. Only two stations are used in each calculation and, since the stations are permanently positioned at known locations, the distance between these stations is always known and can be readily included into the computations.
When a radar electronic positioning system is utilized for guiding airplanes, for example, in crop dusting, spraying forests, or in any other application where a uniform flight pattern is required, reference stations must be set up for each operation and the distance between the reference stations (the baseline) must be included. If the operation includes a large area the operator may have to frequently reload the airplane with spray and fuel. When the reloading is required the operator must leave the pattern. When the reloading is completed it is desirable to return to the exact point at which the operation was interrupted and continue the operation. Overlaps are costly because of the extra spray used and can sometimes be detrimental to the health of plants because of the excess spray. Missed areas can be detrimental to the operation because it leaves insects and/or diseases uncontrolled. In all prior art systems known to us the operator must guess at the correct point or he must fly until all of the indicators read the same as they did when he left the pattern. This is generally very difficult. Further, all of the known prior art systems utilize extremely complex apparatus which is very costly and requires much of the pilots time for setting up the operation and operating during the spraying or the actual flight.